Run of mine (ROM) coal is used for energy production after it is processed. Wet processing can reduce the ash and sulfur content of the coal, but it wets the processed coal. There are many drawbacks to wet processing. For example, the liquid media requires treatment in a wastewater treatment facility. Coal fines and water produce sludge with environmental problems. Some processes use acids to remove contaminants and pollute water. The latent heat of water in wet coal reduces the recoverable energy from the combustion of coal by one to two percent. This reduction in useful energy increases the carbon footprint to produce electrical power. Some 95% of coal processing currently uses wet methods.
A preferred method for processing ROM coal is dry processing. Generally, ROM coal includes a number of rocks of different sizes and compositions (fractions). Their sizes can range from small pebbles (for example 2 mm) to larger rocks (for example 70 mm and even greater) and their composition variable from silicates to iron pyrites. These rocks have a higher density than the coal. Dry processing does not create ecologically undesirable waste or require complex permits. The coal fines, which can be a substantial proportion of the fuel value in the coal, are not affected by dry processing. A commercially useful coal sorter must provide high throughput while it removes rocks and has minimal loss of fuel value. Accordingly, enhancing currently existing dry processing methods and devices is needed.